The present invention relates to a perpendicular magnetization film used as a perpendicular magnetic storage medium which is suitable for high-density recording, and the preparation thereof.
For a high-density magnetic storage, a perpendicular magnetic storage medium is effectively used. A magnetic storage medium used for such a purpose is prepared by the use of magnetic thin film which has an easy magnetization axis perpendicular to a plane of film. For perpendicular magnetic storage, there have been researched a magnetic storage of cobalt-chromium alloy prepared by means of sputtering or vacuum-evaporation method, and also a magnetic storage of barium-ferrite alloy prepared by means of coating or sputtering method. For applying cobalt-chromium thin film to a perpendicular magnetic storage, a structure of single crystal or a structure close to single crystal must be provided. In a process of preparing an alloy having the above structure, a substrate needs to be heated to a temperature of more than 100.degree. C. or in some cases to a temperature of more than 200.degree. C. On the other hand, for applying barium-ferrite thin film to a perpendicular magnetic storage by means of coating method, a barium and ferrite powder consisting of uniform particles of about 0.1 .mu.m in diameter must be provided. It costs much to produce such barium and ferrite powder. Moreover, it is necessary to mix a binder to form a film. In a film containing such a binder, a saturation magnetization becomes smaller depending on a content of a binder, so that capacity of magnetic storage is decreased. In a process of preparing a barium-ferrite film by means of sputtering method, a substrate needs to be heated to a temperature of about 500.degree. C. Thus, a substrate of cheap plastic materials cannot be used.
An object of the present invention is to solve the problem that an ordinary plastic material cannot be used for a substrate of a perpendicular magnetic storage of cobalt and chromium, and that a material of substrate is restricted within expensive polyimides, aluminum, glass, or the like because a substrate must be heated to a temperature of more than 100.degree. C. in a process of preparation thereof. Another object of the invention is to solve the problem that cobalt is rare and expensive resources. Still another object of the invention is to solve the problem that a perpendicular magnetic storage of barium-ferrite alloy has low saturation magnetization compared with cobalt-chromium alloy.
The above and other objects and the advantages of the present invention will become apparent from the following description.